When radio communication in an uplink direction from a radio terminal to a connection destination radio base station is carried out in a radio communication system, interference caused by the radio terminal on a neighboring radio base station (a neighboring base station) is controlled (see Patent Document 1, for example).
The same applies to LTE (Long Term Evolution) which is a 3GPP standard. In the LTE, one radio base station is assumed to control interference received from a radio terminal connected to a neighboring radio base station (interference in the uplink direction from a neighboring cell) by exchanging information on an interference condition called OI (Overload Indicator) between the radio base stations.
Specifically, the one radio base station measures interference power in the uplink direction from the neighboring cell for each radio resource unit called a resource block (RB) and transmits ternary information indicating any of “small interference”, “large interference”, and “very large interference”, for instance, to the neighboring radio base station depending on the interference power. The neighboring radio base station that receives the ternary information can control transmission power (transmission power in the uplink direction) of the connected radio terminal by use of the ternary information. For example, the neighboring radio base station controls the radio terminal upon receipt of the information indicating that the interference power is “very large” in such a manner as to lower the transmission power in the uplink direction, thereby reducing the interference power in the uplink direction on the one radio base station.